Broadband subscriptions, both fixed and mobile, increased just 0.1pc on the previous quarter and stood at 1.6m at the end of March, ComReg reported in its latest market report.
The figures, which predate the launch of next-generation broadband products in recent weeks, show that fixed broadband penetration stood at 24.6pc of the population, rising to 36.4pc when mobile broadband is included.
Average broadband speeds are showing indications of rising, with 21.9pc of all broadband subscriptions equal or greater than 10Mbps, up from 19.1pc a year ago.
The mobile market now accounts for 72.2pc of all voice and internet subscriptions, with fixed-line telephony services accounting for the remaining 27.8pc.
The revenue picture for Irish telecoms
Total quarterly electronic communications revenues were €912.8m, a decrease of 2.1pc compared with last year.
Mobile voice and SMS revenues are decreasing while mobile data revenues are increasing.
Average revenue per user (ARPU) in the first quarter was €28 per month, down from €29 the previous quarter.
ComReg says the drop in ARPU is due to lower-priced mobile plans and increased sales of bundled products.
There were 5.4m mobile phone subscriptions in the Republic of Ireland at the end of March, down 0.5pc on the previous quarter.
Overall, mobile phone penetration currently stands at 118.5pc.